- Larger mirror than HST so more sensitivity (can see fainter stars and galaxies), and better angular resolution (diffraction limit). - Infrared optimized. Because of thermal backgrounds, infrared is best done from space. (HST has some IR capability though)
For example, when I am on the plane, my laptop has no access to the NAS (did I mention that I forgot to rsync before I left). With Dropbox, it syncs seamlessly, and so always has the most recent copy. And then it syncs up automatically when I get back online.
According to the article "the astronomers determined that the galaxy UGC 3789 is 160 million light-years from Earth". This translates to 49 Mpc. According to NED, the velocity (in the Cosmic Microwave Background frame) is 3385 km/s.
Therefore this measurement of the Hubble parameter is then 3385/49 = 69 km/s/Mpc.
(Unfortunately the article does not quote an uncertainty on the 49 Mpc measurement. Because of peculiar velocities, I would estimate that there is at least a 300 km/s uncertainty on the 3385 km/s velocity. )
MoND does a good job of explaining rotation curves of spiral galaxies, but that's about it. It fails on the scales of clusters of galaxies, as even its proponents acknowledge. Nor does it make useful predictions for the growth of large-scale structure.
I have no idea what you mean when you say it explains the same things as the "String Hypothesis."
Actually the orbital velocity is (surprisingly) close to constant, as in most spiral galaxies. In fact, it is these "flat" (i.e. constant as a function of galactocentric radius) rotation curves that were some of the earliest evidence for dark matter.
That having been said, my guess is that the velocities quoted in the press release refer to the Sun's (or more accurately the Local Standard of Rest's) velocity around the Galactic center.
I am an astronomer. I don't know about Duesberg or Velikovsky, but I can tell you that Halton Arp's theories do not agree with the available evidence.
Contrary to the romantic notions of some, there is no "conspiracy" against him. There is a sound, rational reason that he is ignored: its simply that his ideas do not match the observations.
It only took a few minutes of googling to come up with this paper.
Note that "this paper" has not yet been refereed and accepted by a journal. It is conventional, when submitting papers to arxiv, to indicate to what journal the paper has been submitted, whether it has been refereed and accepted or not. There is none of that information here. Normally a paper submitted in March 2008 would have been accepted and published by end of Nov 2008 if it had been. I suspect that it has been rejected.
According to the current theory, dark energy does exist in our solar system, its just that you need many, many more than only 9 decimal places to measure it.
Its repulsive effect however increases with scale, so the larger distances you probe, the easier it is detect.
Except, I don't really see how high energy physics is involved. I mean, it's not as if anybody has proposed a high-energy experiment that could detect it.
Ultimately, there must be a particle-physics-based explanation for Dark Energy, whether from string theory or something other theory.
And just because Dark Energy not accessible via "classical" accelerator experiments, this does not mean that it should not be considered experimental particle physics research. In other words, instead of using a ground-based accelerator, the Universe is the "poor man's" accelerator.
Actually DOE has always been deeply involved in high energy (particle physics) research. They fund a number of accelerators, including Fermilab. Its not clear that any of that research would lead to usable energy sources either.
You can see the Dark Energy research as the intersection of high energy physics (DOE) and cosmology (NASA).
I may run fewer lights, but I still have to run A/C, which is the major hit on my electric bill in the summer.
I think the A/C is the key to this puzzle. More A/C in the summer (clock says 5 PM when you get back from work, but temperature-wise its still 4 PM) morethan cancels out the electricity savings due to lighting.
The observed temperature fluctuations in the Cosmic Microwave Background allow one to determine the statistics of dark matter fluctuations at that time (a few hundred thousand years after the Big Bang) albeit on slightly larger scales, which then become the initial conditions for these simulations.
No one has much clue as the nature of dark matter in the way that we do about standard matter: What happens when it clumps together, does it get hot ? Does that heat help to counteract gravity ? Without knowing fundemental things like this - how is it possible to do detailed simulations ?
Dark matter is postulated to have very simple properties - it interacts only weakly (like neutrinos) which means that collisions between a dark matter particle and any other particles are so rare that they can be ignored.
Consequently, it is actually very easy to put into simulations because the only force that is important is gravity.
So to answer your questions: yes when it clumps together (through gravity) it does get hot, where "heat" means the average velocity of particles with respect to the mean velocity of the clump. This isa consequence of the virial theorem: kinetic energy (heat) balances gravitational potential energy (clumping).
Slashdot Mirror
C'mon mods, seems like a perfectly reasonable comment to me.
- Larger mirror than HST so more sensitivity (can see fainter stars and galaxies), and better angular resolution (diffraction limit).
- Infrared optimized. Because of thermal backgrounds, infrared is best done from space. (HST has some IR capability though)
... so this article is not really journalism, but rather marketing.
Exactly what I was thinking!
Mod parent up please.
What an incoherent rant. Perhaps you should lay off the vino before posting to slashdot.
NAS is not the same.
For example, when I am on the plane, my laptop has no access to the NAS (did I mention that I forgot to rsync before I left). With Dropbox, it syncs seamlessly, and so always has the most recent copy. And then it syncs up automatically when I get back online.
Another me too ... since it syncs Linux/Mac and Windows it was perfect for me. I recently upgraded to the 50Gb plan - cant see myself going back.
( I hardly need the extra referral bonus space now but hey, it doesn't hurt either ... https://www.getdropbox.com/referrals/NTE2MjAzNTk )
According to the article "the astronomers determined that the galaxy UGC 3789 is 160 million light-years from Earth". This translates to 49 Mpc. According to NED, the velocity (in the Cosmic Microwave Background frame) is 3385 km/s.
Therefore this measurement of the Hubble parameter is then 3385/49 = 69 km/s/Mpc.
(Unfortunately the article does not quote an uncertainty on the 49 Mpc measurement. Because of peculiar velocities, I would estimate that there is at least a 300 km/s uncertainty on the 3385 km/s velocity. )
MoND does a good job of explaining rotation curves of spiral galaxies, but that's about it. It fails on the scales of clusters of galaxies, as even its proponents acknowledge. Nor does it make useful predictions for the growth of large-scale structure.
I have no idea what you mean when you say it explains the same things as the "String Hypothesis."
The observed redshift (4.5 in this case) and the Friedmann equation.
No, this was just a little Bang. The big one, we had already found. You can see a picture here.
"9,000 ordinary supernovae" = 9000 x 10^44 Joules =~ 10^48 Joules.
According to Wikipedia, 1 ton (do they mean tonne) of TNT = 4 x 10^9 Joules, so this makes 2 x 10^38 tons of TNT equivalent.
And the largest bomb ever exploded is 5x10^8 tons of TNT.
So this would be ~ 10^30 of those, or around a million Yotta-bombs.
Not sure if that helps.
Actually the orbital velocity is (surprisingly) close to constant, as in most spiral galaxies. In fact, it is these "flat" (i.e. constant as a function of galactocentric radius) rotation curves that were some of the earliest evidence for dark matter.
That having been said, my guess is that the velocities quoted in the press release refer to the Sun's (or more accurately the Local Standard of Rest's) velocity around the Galactic center.
Couldn't find the paper on arxiv.org ...
I am an astronomer. I don't know about Duesberg or Velikovsky, but I can tell you that Halton Arp's theories do not agree with the available evidence.
Contrary to the romantic notions of some, there is no "conspiracy" against him. There is a sound, rational reason that he is ignored: its simply that his ideas do not match the observations.
It only took a few minutes of googling to come up with this paper.
Note that "this paper" has not yet been refereed and accepted by a journal. It is conventional, when submitting papers to arxiv, to indicate to what journal the paper has been submitted, whether it has been refereed and accepted or not. There is none of that information here. Normally a paper submitted in March 2008 would have been accepted and published by end of Nov 2008 if it had been. I suspect that it has been rejected.
According to the current theory, dark energy does exist in our solar system, its just that you need many, many more than only 9 decimal places to measure it.
Its repulsive effect however increases with scale, so the larger distances you probe, the easier it is detect.
Except, I don't really see how high energy physics is involved. I mean, it's not as if anybody has proposed a high-energy experiment that could detect it.
Ultimately, there must be a particle-physics-based explanation for Dark Energy, whether from string theory or something other theory.
And just because Dark Energy not accessible via "classical" accelerator experiments, this does not mean that it should not be considered experimental particle physics research. In other words, instead of using a ground-based accelerator, the Universe is the "poor man's" accelerator.
Actually DOE has always been deeply involved in high energy (particle physics) research. They fund a number of accelerators, including Fermilab. Its not clear that any of that research would lead to usable energy sources either.
You can see the Dark Energy research as the intersection of high energy physics (DOE) and cosmology (NASA).
Don't think so
DLT Tapes ($25 for 40 GB + cost of drive) are now more expensive than hard drives.
They are even deader than spinning disk.
"A toke a day keeps memory loss at bay"
I may run fewer lights, but I still have to run A/C, which is the major hit on my electric bill in the summer.
I think the A/C is the key to this puzzle. More A/C in the summer (clock says 5 PM when you get back from work, but temperature-wise its still 4 PM) morethan cancels out the electricity savings due to lighting.
Figure 1 is the dark matter density.
But the annhiliations, assuming they happen at all, would go as density squared.
The observed temperature fluctuations in the Cosmic Microwave Background allow one to determine the statistics of dark matter fluctuations at that time (a few hundred thousand years after the Big Bang) albeit on slightly larger scales, which then become the initial conditions for these simulations.
No one has much clue as the nature of dark matter in the way that we do about standard matter:
What happens when it clumps together, does it get hot ? Does that heat help to counteract gravity ?
Without knowing fundemental things like this - how is it possible to do detailed simulations ?
Dark matter is postulated to have very simple properties - it interacts only weakly (like neutrinos) which means that collisions between a dark matter particle and any other particles are so rare that they can be ignored.
Consequently, it is actually very easy to put into simulations because the only force that is important is gravity.
So to answer your questions: yes when it clumps together (through gravity) it does get hot, where "heat" means the average velocity of particles with respect to the mean velocity of the clump. This isa consequence of the virial theorem: kinetic energy (heat) balances gravitational potential energy (clumping).
... Klein bottle?